Well known are self-service stores where clients themselves, by means of a scanning device, scan a code of each article selected for purchase and register same in the memory of the scanning device. At the exit of the store, the memory of the scanning device is then coupled to a readout device, which reads the codes registered by the client and subsequently produces a receipt. Thus, long waiting times at the cash points are avoided.
Such stores are for instance described in British patent application 2068132 and in Dutch patent application 8800907.
A problem presenting itself in the known stores is the implementation of an efficient check of the correctness of the registration. According to British patent application 2068132, a check of the correctness of the registration has been made possible by incorporating information about the weight of each article into the code thereof, so that the total weight of all the selected articles can be calculated after the codes thereof have been read out.
Further, a weighing device is present, which weighs the articles when still disposed in a trolley. The weight indicated by the weighing device can subsequently be compared with the total weight calculated.
A disadvantage of this checking method is that it requires special weighing devices which are relatively sizeable and costly. Moreover, such a weight check does not permit a distinction to be made between articles of the same weight but different prices.
According to Dutch patent application 8800907, the number of articles is checked by means of a light barrier above the box of the trolley. Further, in a lock, the codes of a number of articles still disposed in the trolley are optically read and it is checked whether these codes have in fact been registered correctly.
This checking method, too, is rather laborious and requires large investments in trolleys equipped with vulnerable light barriers and locks in which the trolleys can be placed in order to check a number of codes.